"Federer is perhaps still the best tennis player in history, but as a man he's the opposite," Srdjan told Serbian newspaper Kurir.

"He attacked Novak at the Davis Cup in Geneva [in 2006], he realised that he was his successor and was trying to discredit him in every way. Novak's success is an amazing thing and something that one cannot understand."

Djokovic and Federer have not seen eye to eye in the past, with the latter questioning the use of tactical medical timeouts of Djokovic in the same tie, and five years ago Federer was seen telling the Djokovic camp to be quiet after a point.

Srjdan also turned his scathing attack to French Open champion Nadal, saying a friendship which once existed has now disappeared.

"Nadal was his best friend while he was winning. When things changed, they were no longer friends. This is not sport. This is what Novak has in him, but others don't," he added.

Srjdan believes newly-crowned Wimbledon champion and US Open holder Andy Murray is not like Federer and Nadal.

"I have never, not even for a second, felt jealousy from Andy's family. They cannot be best friends as they fight for the most important titles, and lot of money. But they are more than correct rivals," he said.